Portable electronic devices have become ubiquitous in our modern society. For example, people ranging from college students to professionals may simultaneously carry a personal digital assistant (PDA), a mobile telephone, and a digital music player (such as an MP3 player). Even young children are beginning to use mobile telephones and digital music players.
While portable electronic devices are convenient, their very portability creates problems that did not exist with larger, semi-permanently located electronic devices.
First, manufacturers are continuously reducing the size of portable electronic devices, in order to enhance their portability. This size reduction inherently reduces the area available on portable electronic devices to place buttons, knobs, switches, or other controls for operating the electronic device. Second, portable electronic devices frequently are operated while the user is moving. For example, many users will operate a digital music player while running, exercising in a gym, bicycling, skiing, or engaging in some other athletic activity. For most people, this movement prohibits the operation of small controls that require precise hand-eye coordination.